Al2O3绝缘层的AlGaN/GaN MOSHEMT器件研究

在研制AlGaN/GaN HEMT器件的基础上，采用ALD法制备了Al₂O₃ AlGaN/GaN MOSHEMT器件.通过X射线光电子能谱测试表明在AlGaN/GaN异质结材料上成功淀积了Al₂O₃薄膜.根据对HEMT和MOSHEMT器件肖特基电容、器件输出以及转移特性的测试进行分析发现：所制备的Al₂O₃薄膜与AlGaN外延层间界面态密度较小，因而MOSHEMT器件呈现出较 关键词： 2O₃')" href="#">Al₂O₃ ALD GaN MOSHEMT     

MoO3/Al2O3催化剂中Mo分散的正电子研究

用浸渍法制备了一系列不同Mo含量的MoO₃/Al₂O₃催化剂.测量了这些样品的正电子湮没寿命谱(PALS)与符合多普勒展宽(CDB)谱，以研究其孔洞结构以及Mo分散.正电子寿命测量结果表明,Al₂O₃载体中存在两种不同尺寸的孔洞.掺入MoO₃之后,Mo原子主要进入Al₂O₃的大孔中,使孔洞体积减小.符合多普勒展宽谱结果表明，当MoO 关键词： 3/Al₂O₃催化剂')" href="#">MoO₃/Al₂O₃催化剂 正电子湮没寿命谱 符合多普勒展宽 Mo 分散     

Er3+掺杂SiO2复合的Al2O3粉末结构及光致发光特性

采用溶胶-凝胶(sol-gel)工艺制备0.1 mol% Er³⁺掺杂Al₂O₃体系和SiO₂-Al₂O₃复合体系粉末. 实验结果表明：5 mol%的SiO₂复合加入Al₂O₃抑制γ→θ和θ→α相转变. 掺0.1 mol%Er³⁺:Al₂O₃体系粉末，900℃烧结，在1.47—1.63μm波段内光致发光(PL)谱为中心波长1.53 μm、半高宽56 nm的单一宽峰，1000—1200℃烧结，劈裂为多峰PL谱. 掺0.1 mol%Er³⁺:SiO₂-Al₂O₃复合体系粉末，在高达1200℃烧结，仍保持中心波长1.53 μm的单一宽峰PL谱，由于—OH更完全的脱除，PL强度较900℃烧结Al₂O₃体系，SiO₂-Al₂O₃复合体系均提高1个数量级. 关键词： 2-Al₂O₃复合体系')" href="#">SiO₂-Al₂O₃复合体系 掺铒 溶胶-凝胶工艺 光致发光     

电解等离子体法制备Al2O3陶瓷层及其特性研究

利用电弧喷铝并重熔后进行电解等离子体处理(EPP)的方法在Q235钢基体上制备出呈冶金结 合的Al₂O₃陶瓷层.利用XRD，SEM和EDS等手段对陶瓷层的成分和显 微组织进行了分析， 测定了陶瓷层的耐蚀性能和耐磨性能.实验结果表明，陶瓷层主要由α-Al₂O3，γ-Al₂O₃，θ-Al₂O₃以及一 些非晶相组成，组织致密，耐蚀性能和耐磨性能良好. 关键词： 电解等离子体处理 陶瓷层 复合技术 生长机理     

限制电流对Ta/BaTiO3/Al2O3/ITO忆阻器的开关比和稳定性调控

利用磁控溅射技术沉积了Ta/Ba Ti O₃/Al₂O₃/ITO多层薄膜,观察到该结构中的电阻开关现象受到限制电流的调控.在限制电流大小为10^–2 A时,器件中的电阻开关现象达到最优. Ta/Ba Ti O₃/Al₂O₃/ITO多层薄膜的电阻开关具有良好的可重复性和稳定性.本文使用空间限制电流的传导模型对Ta/Ba Ti O₃/Al₂O₃/ITO器件中受限制电流调控的电阻开关传导机理进行了解释.     

TiN/Al2O3纳米多层膜的共格外延生长及超硬效应

采用多靶磁控溅射法制备了一系列具有不同Al₂O₃调制层厚度的TiN/Al₂O₃纳米多层膜. 利用X射线能量色散谱、X射线衍射、扫描电子显微镜、高分辨透射电子显微镜和微力学探针表征了多层膜的成分、微结构和力学性能. 研究结果表明，在TiN/Al₂O₃纳米多层膜中，单层膜时以非晶态存在的Al₂O₃层在厚度小于1.5 nm时因TiN晶体层的模板效应而晶化，并与TiN层形成共格外延生长，相应地，多层膜产生硬度明显升高的超硬效应，最高硬度可达37.9 GPa. 进一步增加多层膜中Al₂O₃调制层的层厚度，Al₂O₃层逐渐形成非晶结构并破坏了多层膜的共格外延生长，使得多层膜的硬度逐步降低. 关键词： 2O₃纳米多层膜')" href="#">TiN/Al₂O₃纳米多层膜 外延生长 非晶晶化 超硬效应     

Cr4+在Al2O3多晶体中的光谱性能研究

采用传统无压烧结工艺制备Cr:Al₂O₃透明多晶陶瓷.测定了其退火前后的吸收光谱和荧光光谱，发现在Al₂O₃六配位的八面体结构中，Cr⁴⁺的荧光发射也处在1100—1600nm波段的红外区间，荧光发射峰位于1223nm附近，类似Cr⁴⁺在四面体中的发光行为.同时由于氧化铝晶格常数较小，晶体场强较强，使Cr⁴⁺:Al₂O_{3< 关键词： 4+')" href="#">Cr⁴⁺ 2}O₃透明陶瓷')" href="#">Cr:Al₂O₃透明陶瓷 光谱性质 八面体     

基于HfO2插层的Ga2O3基金属-绝缘体-半导体结构日盲紫外光电探测器

作为一种新兴的超宽带隙半导体, Ga₂O₃在开发高性能的日盲紫外光电探测器方面具有独特的优势.金属-半导体-金属结构因其制备方法简单、集光面积大等优点在Ga₂O₃日盲紫外光电探测器中得到了广泛的应用.本文在传统的金属-半导体-金属结构Ga₂O₃日盲紫外光电探测器的基础上,利用原子层沉积技术引入高介电性和绝缘性的氧化铪(HfO₂)作为绝缘层和钝化层,制备出带有HfO₂插层的金属-绝缘体-半导体结构的Ga₂O₃日盲紫外光电探测器,显著降低了暗电流,提升了光暗电流比,同时提高了器件的比探测率和响应速度,为未来Ga₂O₃在高性能弱光探测器件制备提供了一种新通用策略.     

关于MgB2/Al2O3超导薄膜电阻转变和各向异性的研究

利用电子束蒸发方法将MgB₂超导薄膜沉积到Al₂O₃(001)衬底上.采用标准的四引线法研究了磁场平行和垂直超导薄膜ab平面下的电阻转变.一个激活能模型 U(T,H)=U₀(1-T/(T_c+δ))ⁿ(1-H/H 关键词： 2/Al₂O₃')" href="#">MgB₂/Al₂O₃ 超导体 电阻转变 各向异性     

非晶态锂离子导体B2O3-0.7Li2O-0.7LiCl-xAl2O3

木文研究了Al₂O₃对B₂O₃-0.7Li₂O-0.7LiCl非晶态的形成和电学性能的影响,我们发现:加入适量的Al₂O₃后,无需借助液氮骤冷技术,直接将熔体倾倒在室温下的紫铜板上就很容易形成大块非晶锂离子导体B₂O₃-0.7Li₂O-0.7LiCl-xAl₂O₃。Al₂O₃的加入使B₂O₃-0.7Li₂O-0.7LiCl的电导率有所降低,但在高温下不太明显,电导激活能略微升高,实验发现:Al₂O₃含量x=0.03是较合适的剂量,较容易形成大块非晶态,对电导率的影响也不大。 关键词：     

磁性隧道结Ni80Fe20/Al2O3/Co的制备和物性

用等离子体氧化形成绝缘层的方法,重复性地制备出了Ｎｉ８０Ｆｅ２０／Ａｌ２Ｏ３／Ｃｏ磁性隧道结。样品的隧道磁电阻（ＴＭＲ）比值在室温下最高可达６．０％,翻转场（ｓｗｉｔｃｈ ｆｉｅｌｄ）可低于８００Ａ／ｍ,平台宽度约２４００Ａ／ｍ。结电阻的变化范围从几百欧姆到几百千欧。     

Inverse TMR in a nominally symmetric CoFe/AlOx/CoFe junction induced by interfacial Fe3O4 investigated by STEM-EELS

We have found inverse tunneling magnetoresistance (TMR) with a non-symmetric bias voltage dependence in a nominally symmetric Si (001)/Ag/CoFe/AlO_x/CoFe/IrMn/Ag magnetic tunnel junction after field cooling. The O K edge fine structure extracted from electron energy loss spectroscopy spectrum images taken at the interfaces of junctions with inverse TMR shows a thin, discontinuous Fe₃O₄ layer at the CoFe/AlO_x interfaces. The Fe L_2,3 edge core level shifts are also consistent with those of Fe₃O₄. We find no Fe₃O₄ layer in junctions with normal TMR. We believe this Fe₃O₄ layer is responsible for the inverse TMR.     

Fe/Al2O3/Fe隧道结特性分析

用离子束溅射方法制备磁性隧道结(MTJ). 研究MTJ样品的隧道结磁电阻(TMR)效应.用X射线 光电子能谱分析了MTJ的软、硬磁层和非磁层及其界面的化学组成与微结构.研究了MTJ的微 结构对氧化铝势垒高度与有效宽度和TMR效应的影响. 关键词： 磁性隧道结 X射线光电子能谱 隧道结磁电阻     

Possible mechanism for tunneling magnetoresistance in La0.9Ba0.1MnO3/Nb-doped SrTiO3 p-n junctions

The observed tunneling magnetoresistance (TMR) effect in La_0.9Ba_0.1MnO₃ (LBMO)/Nb-doped SrTiO₃ (Nb-STO) p⁺-n junctions is investigated and a possible mechanism responsible for the TMR generation is proposed by taking into account the dynamic spin accumulation and paramagnetic magnetization in the Nb-STO layer. Because of carrier diffusion across the dynamic domain boundaries in the Nb-STO layer and spin disordering in the LBMO layer, the tunneling resistance through the junction is high at zero magnetic field. The spin disordering is suppressed upon applying a non-zero magnetic field, which results in the spin-polarized tunneling in this ferromagnetic/depletion layer/dynamic ferromagnetic sandwiched structure and thus the observed TMR effect. The dependence of the TMR effect on the domain size in the LBMO layer, the tunneling current and temperature as well is explained, qualitatively consistent with the experimental observation.     

纳米结构ZnxFe3-xO4-α-Fe2O3多晶材料中的巨隧道磁电阻效应

在具有纳米绝缘层的多晶锌铁氧体体系中,当晶界为α-Fe₂O₃纳米量级(6—7nm)的绝缘层时,则构成(Zn_xFe_3-xO₄)-α-Fe₂O₃非均匀体,高分辨电子显微镜已证实了这种微结构,该体系在0.5T磁场、4.2K温度下,磁电阻效应可达1280%,300℃下为158%. 关键词： 隧道磁电阻效应 锌铁氧体 纳米结构     

Observation of a tunneling magnetoresistance effect in magnetic tunneling junctions with a high resistance ferromagnetic oxide Fe2⋅5Mn0⋅5O4 electrode

A high resistance ferromagnetic oxide Fe_2⋅5Mn_0⋅5O₄ (FMO) property as a novel spin injector was investigated with a structure of a magnetic tunneling junction (MTJ) composed of FMO/Al-O/Ni₈₀Fe₂₀, in order to reduce an impedance mismatch problem on molecular spintronics. A tunneling magnetoresistance (TMR) effect in the MTJs was observed. The maximum TMR ratio observed in the MTJs was approximately 0.85% at room temperature (RT), and the spin-polarization of FMO was estimated to be at least 0.94% at RT.     

Magneto-transport and magnetic properties of (1-x)La0.7Ca0.3MnO3+xAl2O3 composites

We report magneto-transport and magnetic properties of (1-x)La_0.7Ca_0.3MnO₃+xAl₂O₃ composites synthesized through a solid-state reaction method combined with a high energy milling method. Most interestingly, the effective magnetic anisotropy is found to decrease with increase in the non-magnetic insulating Al₂O₃ phase fraction in the composites. In addition, we observed that the magnitude of low-field magnetoresistance arising from spin-polarized tunneling of conduction electrons, as well as that of high-field magnetoresistance, displays a Curie-Weiss law-like behavior. Finally, we found that the temperature dependence of low and high-field magnetoresistance is controlled predominantly by the nature of temperature response of surface magnetization of the particles.     

Investigation of interface characteristics of Al2O3/Si under various O2 plasma exposure times during the deposition of Al2O3 by PA-ALD

Plasma-assisted atomic layer deposition (PA-ALD) is more suitable than thermal atomic layer deposition (ALD) for mass production because of its faster growth rate. However, controlling surface damage caused by plasma during the PA-ALD process is a key issue. In this study, the passivation characteristics of Al₂O₃ layers deposited by PA-ALD were investigated with various O₂ plasma exposure times. The growth per cycle (GPC) during Al₂O₃ deposition was saturated at approximately 1.4?Å/cycle after an O₂ plasma exposure time of 1.5?s, and a refractive index of Al₂O₃ in the range of 1.65–1.67 was obtained. As the O₂ plasma exposure time increased in the Al₂O₃ deposition process, the passivation properties tended to deteriorate, and as the radio frequency (RF) power increased, the passivation uniformity and the thermal stability of the Al₂O₃ layer deteriorated. To study the Al₂O₃/Si interface characteristics, the capacitance-voltage (C-V) and the conductance-voltage (G-V) were measured using a mercury probe, and the fixed charge density (Q_f) and the interface trap density (D_it) were then extracted. The Q_f of the Al₂O₃ layer deposited on a Si wafer by PA-ALD was almost unaffected, but the D_it increased with O₂ plasma exposure time. In conclusion, as the O₂ plasma exposure time increased during Al₂O₃ layer deposition by PA-ALD, the Al₂O₃/Si interface characteristics deteriorated because of plasma surface damage.     

Interfacial reactions and oxidation behavior of Al2O3 and Al2O3/Al coatings on an orthorhombic Ti2AlNb alloy

The uniform and dense Al₂O₃ and Al₂O₃/Al coatings were deposited on an orthorhombic Ti₂AlNb alloy by filtered arc ion plating. The interfacial reactions of the Al₂O₃/Ti₂AlNb and Al₂O₃/Al/Ti₂AlNb specimens after vacuum annealing at 750 °C were studied. In the Al₂O₃/Ti₂AlNb specimens, the Al₂O₃ coating decomposed significantly due to reaction between the Al₂O₃ coating and the O-Ti₂AlNb substrate. In the Al₂O₃/Al/Ti₂AlNb specimens, a γ-TiAl layer and an Nb-rich zone came into being by interdiffusion between the Al layer and the O-Ti₂AlNb substrate. The γ-TiAl layer is chemically compatible with Al₂O₃, with no decomposition of Al₂O₃ being detected. No internal oxidation or oxygen and nitrogen dissolution zone was observed in the O-Ti₂AlNb alloy. The Al₂O₃/Al/Ti₂AlNb specimens exhibited excellent oxidation resistance at 750 °C.